Heat dissipation apparatus incorporating airflow generator

ABSTRACT

A heat dissipation apparatus includes a heat sink defining a plurality of air passages therein, and an airflow generator arranged on the heat sink and including a plurality of airflow-generating units. Each airflow-generating unit includes a casing, and a vibration diaphragm and a driving member arranged in the casing. The vibration diaphragm divides an inner space of the casing into first and second chamber isolated from each other. The second chamber communicates with the exterior via an orifice defined in a bottom wall of the casing. The driving member is capable of vibrating the vibration diaphragm when alternating voltage is applied thereto. When the driving member vibrates the vibration diaphragm towards the bottom wall of the casing, the vibration diaphragm compresses the air inside the second chamber of the casing towards the orifice, generating airflow from the orifice to the air passages of the heat sink.

BACKGROUND

1. Technical Field

The disclosure generally relates to heat dissipation; and moreparticularly to a heat dissipation apparatus incorporating an airflowgenerator.

2. Description of Related Art

With developments in electronic components such as central processingunits (CPUs), such components are nowadays capable of operating at veryhigh speeds. The amount of heat generated by such components duringnormal operation is commensurately large. If not quickly removed from aCPU, this generated heat may cause the CPU to become overheated andfinally affect its workability and stability.

In order to remove the heat from a CPU and hence ensure normaloperation, a heat dissipation device is usually provided. A frequentlyused heat dissipation device includes a fan, a heat sink arranged at anoutlet of the fan, and a heat pipe thermally connecting the heat sinkwith the CPU. Heat generated by the CPU is transferred to fins on theheat sink via the heat pipe. Airflow from the fan crosses the fins ofthe heat sink and removes the heat from the fins to the exterior of thesystem.

However, the fan includes an impeller that is driven by an electricmotor. When the fan runs at high speed, it generates noise. In addition,the impeller of the fan usually increases the size of the heatdissipation device, compromising efforts to limit the size of thecorresponding electronic product.

What is needed, therefore, is a means to overcome the describedlimitations.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the present embodiments can be better understood withreference to the following drawings. The components in the drawings arenot necessarily drawn to scale, the emphasis instead placed upon clearlyillustrating the principles of the present embodiments. Moreover, in thedrawings, like reference numerals designate corresponding partsthroughout the several views.

FIG. 1 is an isometric, assembled view of a heat dissipation apparatusin accordance with a first exemplary embodiment of the presentdisclosure.

FIG. 2 is an exploded view of the heat dissipation apparatus of FIG. 1.

FIG. 3 is an exploded view of an airflow generator of the heatdissipation apparatus of FIG. 2.

FIG. 4 is an inverted view of FIG. 3.

FIG. 5 is a cross-section of the heat dissipation apparatus of FIG. 1,taken along a line V-V thereof.

FIG. 6 is a schematic view corresponding to FIG. 5, showing a firststage of operation of one airflow-generating unit of the heatdissipation apparatus of FIG. 1.

FIG. 7 is similar to FIG. 6, but showing a second stage of operation ofthe airflow-generating unit.

FIG. 8 is similar to FIG. 7, but showing a third stage of operation ofthe airflow-generating unit.

FIG. 9 is a cross-section of a heat dissipation apparatus in accordancewith a second exemplary embodiment of the present disclosure.

DETAILED DESCRIPTION

Referring to FIGS. 1-2, a heat dissipation apparatus 100 according to afirst exemplary embodiment of the present disclosure is shown. The heatdissipation apparatus 100 includes a heat sink 10, and an airflowgenerator 20 mounted on the heat sink 10. In a typical application, aheat source (not shown), such as an electronic component, generatesheat, and such heat is transferred from the heat source to the heat sink10.

The heat sink 10 includes a rectangular base 11 for contacting the heatsource to absorb heat therefrom, and a plurality of spaced fins 12formed on the base 11. A plurality of air passages 13 is defined betweenadjacent fins 12. The heat sink 10 forms four mounting portions 14 atfour corners thereof. Each mounting portion 14 defines a mounting hole15 therein.

Referring also to FIGS. 3-4, the airflow generator 20 includes a shell30 and a plurality of airflow-generating units 40 arranged in the shell30. The shell 30 includes a base plate 31 and a cover 32 connected tothe base plate 31. The cover 32 includes a generally rectangular topplate 321 having four cutouts 3211 defined at four corners thereof, suchthat the top plate 321 has a polygonal shape. The cover 32 also includesa polygonal-shaped peripheral sidewall 322 extending down from aperipheral edge of the top plate 321, and four fixing portions 323formed at a bottom end of the sidewall 322 at the four corners of thecover 32 where the cutouts 3211 are. Each fixing portion 323 forms asupporting post 325 on a bottom surface thereof, and defines a throughhole 324 therein. The through hole 324 spans though the fixing portion323 including the supporting post 325.

When the airflow generator 20 is mounted to the heat sink 10, thesupporting posts 325 of the cover 32 rest on and are supported by themounting portions 14 of the heat sink 10, with the through holes 324 ofthe fixing portions 323 of the cover 32 aligned with correspondingmounting holes 15 of the mounting portions 14 of the heat sink 10. Fourfixing members 101 such as screws respectively extend through thethrough holes 324 of the cover 32 and are engaged in the mounting holes15 of the heat sink 10, thereby fixing the airflow generator 20 on theheat sink 10. The mounting portions 14 of the heat sink 10 are spacedfrom the fixing portions 323 of the cover 32 by the supporting posts 325disposed therebetween. In other words, the airflow generator 20 isspaced from the heat sink 10 a predetermined distance.

Referring also to FIG. 5, the cover 32 and the base plate 31cooperatively define a cavity (not labeled) therebetween, in whichairflow-generating units 40 are received and arrayed. Eachairflow-generating unit 40 includes a casing 41, and a vibrationdiaphragm 42 and a driving member 43 received in the casing 41. Thecasing 41 is cuboid, and has an opening 44 (see FIG. 4) at a bottom sidethereof facing the heat sink 10. The base plate 31 is attached to bottomends of the casings 41 of the airflow-generating units 40. The baseplate 31 is a single body of material, and functions as bottom walls ofthe casings 41 of the airflow-generating units 40, and defines aplurality of orifices 311 therein corresponding to theairflow-generating units 40. Alternatively, the base plate 31 can bedivided into a plurality of pieces corresponding to theairflow-generating units 40. Each piece defines an orifice therein, andis attached to a bottom end of the casing 41 of a correspondingairflow-generating unit 40, functioning as a bottom wall of the casing41 of the airflow-generating unit 40.

The vibration diaphragm 42 of each airflow-generating unit 40 is elasticmaterial, such as rubber, flexible resin or a thin metal sheet. Thevibration diaphragm 42 is horizontally mounted in the casing 41. Aninner space of the casing 41 is divided into a first chamber 411 and asecond chamber 412 by the vibration diaphragm 42. The first chamber 411and the second chamber 412 are isolated from each other, and are locatedat top and bottom sides of the vibration diaphragm 42, respectively. Thesecond chamber 412 communicates with the exterior via one correspondingorifice 311 of the base plate 31.

The driving member 43 is adapted for vibrating the vibration diaphragm42 up and down. In this embodiment, the driving member 43 is apiezoelectric element (hereinafter indicated also by numeral 43). Thepiezoelectric element 43 is attached to a middle portion of thevibration diaphragm 42 so as to vibrate substantially perpendicular tothe vibration diaphragm 42 when an alternating voltage is applied to thepiezoelectric element 43. The piezoelectric element 43 is made ofpiezoelectric ceramic. Through holes (not labeled) are defined in twoopposite of the sidewalls 322 of the cover 32 and in sidewalls of thecasings 41, for extension of wires 430 therethrough to electricallyconnect the piezoelectric elements 43 on the vibration diaphragms 42 ofthe airflow-generating units 40 with an external power supply (notshown).

In operation of the heat dissipation apparatus 100, the external powersupply provides an alternating voltage to the piezoelectric element 43of each airflow-generating unit 40 via the corresponding wire 430. As aresult of the reverse piezoelectric effect, the piezoelectric element 43produces alternating expansion and retraction, vibrating the vibrationdiaphragm 42 up and down. When the piezoelectric element 43 vibrates thevibration diaphragm 42 downwardly, the vibration diaphragm 42 compressesthe air inside the second chamber 412 and drives the air towards thecorresponding orifice 311 of the base plate 31, generating airflow fromthe orifice 311 towards the corresponding air passages 13 of the heatsink 10. The airflow along the air passages 13 of the heat sink 10removes heat present in the fins 12.

Referring to FIGS. 6-8, an airflow-generating process of eachairflow-generating unit 40 in one vibrating period is as follows:

The airflow-generating process is divided into a first stage, a secondstage and a third stage. In the first stage, the external power supplyprovides a negative/positive voltage to the piezoelectric element 43 viathe wire 430, and the piezoelectric element 43 drives the vibrationdiaphragm 42 towards the base plate 31. The air inside the secondchamber 412 is compressed by the vibration diaphragm 42 and flowstowards the corresponding orifice 311 of the base plate 31. Referring toFIG. 6, when the vibration diaphragm 42 moves from an originallyhorizontal position to a curved position indicated by broken lines A, afirst airflow 102 is generated from the corresponding orifice 311 of thebase plate 31 towards the corresponding air passages 13 of the heat sink10. The first airflow 102 along the air passages 13 of the heat sink 10results in heat exchange from the fins 12 to the air, and the heat ofthe fins 12 is thereby removed.

In the second stage of the airflow-generating process, thenegative/positive voltage supplied to the piezoelectric element 43 isinverted to a positive/negative voltage, such that the piezoelectricelement 43 drives the vibration diaphragm 42 away from the base plate31. Referring to FIG. 7, when the vibration diaphragm 42 returns fromthe curved position indicated by broken lines A (see FIG. 6) back to thehorizontal position, the air outside the casing 41 and around thecorresponding orifice 311 is drawn into the air passages 13 of the heatsink 10, generating a second airflow 103 along the air passages 13 ofthe heat sink 10, at a flow rate about ten times that of the firstairflow 102.

In the third stage of the airflow-generating process, the vibrationdiaphragm 42, as shown in FIG. 8, continues to move farther way from thebase plate 31 until it reaches the curved position indicated by brokenline B. During this stage, the volume of the second chamber 412 isexpanded, such that cool air (indicated by arrows 33) outside the casing41 and around the corresponding orifice 311 of the base plate 31 isdrawn into the second chamber 412 of the casing 41. Then thepositive/negative voltage supplied to the piezoelectric element 43 isinverted to the negative/positive voltage, and the first stage of theairflow-generating process begins again.

In each airflow-generating unit 40, under the alternating voltage, thepiezoelectric element 43 vibrates the vibration diaphragm 42 toperiodically compress the air inside the second chamber 412 of thecasing 41, generating airflow from the orifice 311 towards the airpassages 13 of the heat sink 10. In addition, by supplying alternatingvoltages of different frequencies, the flow rate of the airflowgenerated by the airflow-generating unit 40 can be adjusted to meetdifferent cooling requirements.

In summary, in the heat dissipation apparatus 100, the heat transferredto the fins 12 of the heat sink 10 is dissipated from the fins 12 by theoperation of the airflow generator 20. The number of airflow-generatingunits 40 of the airflow generator 20 can be chosen to meet the coolingrequirements of a particular application. Further, no motor or impellerof a fan is used in the heat dissipation apparatus 100. Thus the heatdissipation apparatus 100 can have a small size and quiet operation.

Referring to FIG. 9, a heat dissipation apparatus 100 a according to asecond exemplary embodiment of the present disclosure is shown. The heatdissipation apparatus 100 a includes the above-described heat sink 10,and an airflow generator 20 a mounted on the heat sink 10. The airflowgenerator 20 a includes the above-described shell 30, and a plurality ofairflow-generating units 40 a arranged in the shell 30. The differencebetween each airflow-generating unit 40 a and each airflow-generatingunit 40 of the heat dissipation apparatus 100 lies in a driving member43 a of the airflow-generating unit 40 a.

In this embodiment, the driving member 43 a is received in the firstchamber 411 of the casing 41. The driving member 43 a includes a movablemagnet 431 attached to a middle of a top surface of the vibrationdiaphragm 42, and a stationary magnet 433 attached to an inner surfaceof a top wall of the casing 41. The movable magnet 431 and thestationary magnet 433 face each other, and are spaced apart from eachother.

The movable magnet 431 of the driving member 43 a is an electromagnet,and includes a thin iron core 4311 and a wire coil 4312 disposed aroundthe iron core 4311. The iron core 4311 is made of a material which canbe easily magnetized and demagnetized, such as soft iron or siliconsteel. The wire coil 4312 is attached on the vibration diaphragm 42 andsurrounds and is spaced from the iron core 4311. Alternatively, the wirecoil 4312 can be directly wound on and around the iron core 4311. Whenthe airflow-generating units 40 a are arranged in the shell 30, the wirecoils 4312 of the movable magnets 431 of the airflow-generating units 40a are connected to each other in series via electric wires (not shown),and are connected to an external power supply (not shown).

In operation of each airflow-generating unit 40 a, the external powersupply provides an alternating voltage to the wire coil 4312 of themovable magnet 431 of the driving member 43 a. When current travelsthrough the wire coil 4312 of the movable magnet 431 of the drivingmember 43 a, the iron core 4311 of the movable magnet 431 is magnetizedto create a larger magnetic field that extends into the space around theiron core 4311. The polarity of the magnetized movable magnet 431 isdetermined by the direction of the current through the wire coil 4312.The direction of the current through the wire coil 4312 is periodicallyalternated, so that the polarity of the magnetized movable magnet 431 iscorrespondingly periodically inverted. Accordingly, the magnetizedmovable magnet 431 and the stationary magnet 433 of the driving member43 a mutually attract or repel each alternately, vibrating the vibrationdiaphragm 42 up and down. When the movable magnet 431 of the drivingmember 43 a vibrates the vibration diaphragm 42 downwardly, thevibration diaphragm 42 compresses the air inside the second chamber 412and drives the air towards the corresponding orifice 311 of the baseplate 31, generating airflow from the orifice 311 of the base plate 31towards the corresponding air passages 13 of the heat sink 10. Theairflow along the air passages 13 of the heat sink 10 removes heatpresent in the corresponding fins 12.

When the alternating voltage is supplied to the iron core 4311 of themovable magnet 431 of the driving member 43 a of each airflow-generatingunit 40 a, airflow is generated according to substantially the sameprocess as shown in FIGS. 6-8.

In each airflow-generating unit 40 a, under the alternating voltage, thedriving member 43 a vibrates the vibration diaphragm 42 to periodicallycompress the air inside the second chamber 412 of the casing 41, therebyperiodically generating airflow from orifice 311 towards the airpassages 13 of the heat sink 10. By supplying alternating voltages ofdifferent frequencies, the flow rate of the airflow generated by theairflow-generating unit 40 a can be adjusted to meet different coolingrequirements.

Alternatively, the positions of the movable magnet 431 and thestationary magnet 433 of the driving member 43 a can be exchanged.

It is to be understood, however, that even though numerouscharacteristics and advantages of the present embodiments have been setforth in the foregoing description, together with details of thestructures and functions of the embodiments, the disclosure isillustrative only, and changes may be made in detail, especially inmatters of shape, size, and arrangement of parts within the principlesof the disclosure to the full extent indicated by the broad generalmeaning of the terms in which the appended claims are expressed.

1. An airflow generator, comprising: at least one airflow-generatingunit, comprising: a casing defining an inner space therein, the casingcomprising a bottom wall defining an orifice therein; a vibrationdiaphragm arranged in the casing, the vibration diaphragm dividing theinner space of the casing into a first chamber and a second chamberisolated from each other, the second chamber communicating with anexterior of the casing via the orifice of the bottom wall of the casing;and a driving member received in the casing, capable of vibrating thevibration diaphragm in directions substantially perpendicular to thevibration diaphragm when alternating voltage is applied to the drivingmember, wherein when the driving member vibrates the vibration diaphragmtowards the bottom wall of the casing, the vibration diaphragmcompresses the air inside the second chamber of the casing and drivesthe air towards the orifice, generating an airflow from the orifice tothe exterior of the casing.
 2. The airflow generator of claim 1, whereinthe driving member comprises a piezoelectric element attached to thevibration diaphragm.
 3. The airflow generator of claim 1, wherein thedriving member comprises a movable magnet attached to the vibrationdiaphragm, and a stationary magnet attached to a top wall of the casingfacing the vibration diaphragm, one of the movable magnet and thestationary magnet is a permanent magnet, and the other one of themovable magnet and the stationary magnet is an electromagnet.
 4. Theairflow generator of claim 3, wherein the movable magnet is anelectromagnet, and the stationary magnet is a permanent magnet.
 5. Theairflow generator of claim 4, wherein the movable magnet comprises amovable iron core attached to the vibration diaphragm and a wire coildisposed around the iron core.
 6. The airflow generator of claim 1,further comprising a cover, in which the at least one airflow-generatingunit is mounted.
 7. The airflow generator of claim 1, wherein theairflow generator comprises a plurality of the airflow-generating units,and the bottom walls of the casings of the airflow-generating units areintegrally formed together as a single body of material.
 8. A heatdissipation apparatus, comprising: a heat sink defining a plurality ofair passages therein; and an airflow generator arranged on the heatsink, the airflow generator comprising a plurality of airflow-generatingunits arranged in an array, each of the airflow-generating unitscomprising: a casing comprising a bottom wall adjacent to the heat sink;a vibration diaphragm arranged in the casing, the vibration diaphragmdividing an inner space of the casing into a first chamber and a secondchamber isolated from each other, the second chamber being locatednearer to the heat sink and communicating with an exterior of the casingvia an orifice defined in the bottom wall; and a driving member receivedin the casing, capable of vibrating the vibration diaphragm indirections substantially perpendicular to the vibration diaphragm whenalternating voltage is applied to the driving member, wherein when thedriving member vibrates the vibration diaphragm towards the bottom wallof the casing, the vibration diaphragm compresses the air inside thesecond chamber of the casing and drives the air towards the orifice,generating an airflow from the orifice to at least one of the airpassages of the heat sink.
 9. The heat dissipation apparatus of claim 8,wherein the driving member comprises a piezoelectric element attached tothe vibration diaphragm.
 10. The heat dissipation apparatus of claim 8,wherein the driving member comprises a movable magnet attached to thevibration diaphragm, and a stationary magnet attached to a wall of thecasing facing the vibration diaphragm, one of the movable magnet and thestationary magnet is a permanent magnet, and the other one of themovable magnet and the stationary magnet is an electromagnet.
 11. Theheat dissipation apparatus of claim 10, wherein the movable magnet is anelectromagnet, and the stationary magnet is a permanent magnet.
 12. Theheat dissipation apparatus of claim 11, wherein the movable magnetcomprises a movable iron core attached to the vibration diaphragm and awire coil disposed around the iron core.
 13. The heat dissipationapparatus of claim 8, further comprising a cover, in which theairflow-generating units are mounted.
 14. The heat dissipation apparatusof claim 13, wherein the cover comprises a top plate and a sidewallextending down from a peripheral edge of the top plate.
 15. The heatdissipation apparatus of claim 14, wherein the heat sink comprises abase and a plurality of spaced fins formed on the base, and the airpassages are defined between adjacent fins.
 16. The heat dissipationapparatus of claim 15, wherein the heat sink comprises a plurality ofmounting portions, the cover has a plurality of fixing portionscorresponding to the mounting portions of the heat sink, and themounting portions of the heat sink are spaced from the fixing portionsof the cover by a plurality of supporting posts disposed therebetween.17. The heat dissipation apparatus of claim 8, wherein the bottom wallsof the casings of the airflow-generating units are integrally formed asa single piece.
 18. An airflow generator, comprising: a shell comprisinga base plate and a cover connected to the base plate, the cover and thebase plate cooperatively defining a cavity therebetween, the base platedefining a plurality of orifices therein; and a plurality ofairflow-generating units arranged in the cavity and locatedcorresponding to the orifices of the base plate, each of theairflow-generating units comprising: a casing defining an inner spacetherein; a vibration diaphragm arranged in the casing, the vibrationdiaphragm dividing the inner space of the casing into a first chamberand a second chamber isolated from each other, the second chamber beinglocated adjacent to the base plate and communicating with an exterior ofthe casing via a corresponding orifice of the base plate; and a drivingmember received in the casing, capable of vibrating the vibrationdiaphragm in directions substantially perpendicular to the vibrationdiaphragm when alternating voltage is applied to the driving member,wherein when the driving member vibrates the vibration diaphragm towardsthe bottom wall of the casing, the vibration diaphragm compresses theair inside the second chamber of the casing and drives the air towardsthe corresponding orifice, generating an airflow from the correspondingorifice to the exterior of the casing.
 19. The airflow generator ofclaim 18, wherein the driving member comprises a piezoelectric elementattached to the vibration diaphragm.
 20. The airflow generator of claim18, wherein the driving member comprises a movable magnet attached tothe vibration diaphragm, and a stationary magnet attached to a wall ofthe casing facing the vibration diaphragm, one of the movable magnet andthe stationary magnet is a permanent magnet, and the other one of themovable magnet and the stationary magnet is an electromagnet.